In recent years, the demand for biologically synthesized L-cysteine as a raw material has increased in various industries such as foods, medicines, and cosmetics, and the consumer demand for environmentally friendly biological materials has increased.
L-cysteine is a sulfur-containing non-essential amino acid and has been extracted from human or animal hair by acid hydrolysis and electro-reduction methods. However, industrially, these conventional methods have a problem in that the amount of waste to be disposed and the production cost increase. Socially, these methods cause severe environmental pollution and pose issues related to the use of raw materials of animal origin.
In the current global market, L-cysteine is mostly produced in China and exported overseas. In Korea, the demand for and imports of L-cysteine are increasing, but there is no company that produces L-cysteine.
Due to the absence of L-cysteine production technology in the country, the development of L-cysteine production technology based on environmentally friendly biological materials to replace the Chinese physicochemical treatment method for producing L-cysteine is expected to make it possible to supply L-cysteine as raw material to various industrial field, and the demand for the technology is increasing.
In conventional methods of producing L-cysteine using microorganisms, the synthesis of L-cysteine is limited due to the feedback inhibition regulation present in the amino acid and sulfur metabolic pathways, and thus techniques for biologically producing L-cysteine have limitations such as low productivity (Denk D and Böck A. J. general microbiology (1987) 133:515-525; Nakamori S et al., Appl Environ Microb (1998) 64:1607-1611; Takagi H, Kobayashi C, et al., FEBS Letters (1999) 452:323-327; Takagi H, et al., FEMS microbiology letters (1999) 179:453-459; Wirtz M, et al., Amino acids (2003) 24:195-203; Nakatani T et al., Microbial cell factories (2012) 11:62).
Accordingly, the present inventors have made extensive efforts to develop a technology capable of producing a large amount of L-cysteine by microbial fermentation, and as a result, have found that when an L-cysteine-producing mutant microorganism having introduced therein cysE, cysK and cysR, which are enzymes involved in the L-cysteine metabolic pathway, is used, a sulfur source essential for the synthesis of L-cysteine in the microorganism can be continuously supplied to greatly increase L-cysteine production, thereby completing the present invention.